Chapter 6

A single motor neuron and all the muscle cells it stimulates is called a. the sarcoplasmic reticulum. b. a neuromuscular junction. c. a motor unit. d. summation.

In a muscle, energy is stored in the form of a. creatine phosphate. b. ADP. c. myosin. d. glucose.

The __________ are dark bands at the ends of each sarcomere a. \(\mathrm{T}\) tubules b. myosin heads c. \(Z\) lines d. myofilaments

After heavy exercise, _________ help(s) repay the oxygen debt. a. breathing b. stretching c. myosin d. calcium ions

What causes the release of calcium ions from the sarcoplasmic reticulum? a. an increase in calcium ions within the T tubules b. the formation of cross-bridges c. an action potential d. contraction of a sarcomere

The thin filaments consist of a. actin. b. myosin. c. troponin. d. Z lines.

Myoglobin is a. the major component of the thick filament. b. an oxygen-binding molecule in muscle cells. c. released at the neuromuscular junction. d. the molecule that locks the actin-binding site.

What is the smallest functional unit of contraction? a. fiber b. sarcomere c. filament d. myofibril

What type of contraction is characterized by a rapid, jerky response to a single stimulus? a. summation b. treppe c. tonic d. twitch

The function of the transverse tubules (T tubules) is to a. distribute a supply of calcium ions through the muscle fiber. b. conduct action potentials to the interior of the muscle fiber. c. distribute a supply of glycogen throughout the muscle sarcoplasm. d. transport ATP molecules out of the mitochondria throughout the sarcoplasm.

Each myosin head has a. a binding site for an ATP molecule. b. a binding site for an actin molecule. c. the ability to swivel when powered by ATP. d. all of the above

The contractile unit of a muscle is called a/an __________.